I use a PVC 2" to 1 1/2" reducer that fits inside the 4" to 2" reducer those cost like $1 and i don't have to cut any 2" pipe. I would guess the hole is to screw the feeder to the round wood base.
Got here numerous times. From searches such as ‘chicken coop plans’, ‘roll away egg box slope’, ‘panting chickens’, ‘DIY chicken feeder’ the list goes on. Anything chicken related I usually find a link to here within the top 5 results.
(1) Are you new to chickens / when did you first get chickens?
When I was a kid my aunt/uncle had many chickens so I was around them but never really involved. So... not 100% lost but still a newbie!
Had my own chickens two months or so now.
(2) How many chickens do you have right now?
21...